Orthogonal frequency division multiplexing system with dynamically scalable operating parameters and method thereof

• US 6,175,550 B1
• Filed: 04/01/1997
• Issued: 01/16/2001
• Est. Priority Date: 04/01/1997
• Status: Expired due to Term

• Current Assignee: MOSAID Technologies Inc. (f/k/a Conversant Intellectual Property Management)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: van Nee, Richard D. J.
• Primary Examiner(s): O'Neill, Michael
• Assistant Examiner(s): Nguyen, Kim T.
• Application Number:
  US08/834,684
• Time in Patent Office: 1,386 Days
• Field of Search: 370/204, 370/205, 370/206, 370/207, 370/208, 370/212, 370/213, 370/215, 370/482, 370/543, 370/210, 370/252, 370/465, 370/468, 375/260, 375/331, 375/355, 375/244, 375/226, 375/261
• US Class Current: 370/206
• CPC Class Codes: H04L 1/0002 by adapting the transmission rate
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0007 by modifying the frame length
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0025 Transmission of mode-switching indication
• CPC Class Codes: H04L 27/2614 Peak power aspects
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0044 allocation of payload
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling

Abstract

The scaleable OFDM system according to the principles of the present invention provides increased flexibility and adaptability by providing scaling of the operating parameters and/or characteristics for the OFDM system. For example, control circuitry can scale the bit rate by scaling of the OFDM symbol duration, the number of carriers and/or the number of bits per symbol per carrier. Scaleability permits the scaleable OFDM system to operate in various communications environments requiring various operating parameters and/or characteristics. By scaling the operating parameters and/or characteristics of the OFDM system when control circuitry determines that different operating parameters and/or characteristics are necessary or advantageous, the control circuitry can dynamically change the operating parameters and/or characteristics, thereby providing compatibility or the desired performance. For example, by dynamically scaling the bit rate, widely varying signal bandwidths, delay spread tolerances and signal-to-noise ratio (SNR) requirements can be achieved. As such, a scaleable OFDM system is particularly suitable for application in mobile, wireless communication devices, which support a variety of services, in a variety of environments, indoor as well as outdoor and in radio channels with differing bandwidths.

Claims

1. A method for providing communication signals according to operating parameters using orthogonal frequency division multiplexing (OFDM), said operating parameters including symbol duration, guard time interval, number of OFDM carriers, and number of bits per symbol per OFDM carrier, said method comprising the step of:

receiving a feedback signal from a receiver;

determining that an operating characteristic of said method should be scaled from a first level to a second level based on said feedback signal received from said receiver, said operating characteristic being at least one of transmission rate, signal-to-noise ratio, and delay-spread tolerance; and

dynamically scaling at least one of said operating parameters for said method to achieve an operating characteristic of said second level by adaptively selecting one of a plurality of operating parameter scaling options in accordance with said determining step.

2. The method of claim 1 further comprising the steps of:

providing said communication signals at a data rate; and

dynamically changing said data rate.

3. The method of claim 1 further including the step of providing OFDM symbols from said communication signals, and wherein said step of dynamically scaling includes the step of:

dynamically changing symbol duration for said OFDM symbols.

4. The method of claim 3 wherein said step of dynamically changing further includes the step of:

transforming said communication signals into an OFDM symbol using a fourier transformation; and

altering a time base for said fourier transformation.

5. The method of claim 1 further including the step of providing OFDM symbols from said communication signals, and wherein said step of dynamically scaling includes the step of:

dynamically changing the number of carriers for said OFDM symbols.

6. The method of claim 5 wherein said step of dynamically scaling includes the step of:

transforming data inputs onto a subset of the maximum number of said carriers.

7. The method of claim 5 wherein said step of dynamically scaling includes the steps of:

transforming a subset of data inputs from said communication signals onto said carriers; and

setting the remaining data inputs to zero.

8. The method of claim 1 wherein said step of dynamically scaling includes the steps of:

coding communication signals according to a coding rate; and

dynamically changing said coding rate.

9. The method of claim 1 wherein said step of dynamically scaling includes the steps of:

modulating carriers according to a first modulation scheme; and

dynamically changing said first modulation scheme to a second modulation scheme.

10. The method of claim 1 further including the steps of:

transmitting OFDM symbols at an uplink data rate; and

receiving communication signals at a downlink data rate.

11. The method of claim 10 further including the steps of:

dynamically changing said downlink data rate.

12. The method of claim 10 further including the step of:

selecting a downlink data rate different from said uplink data rate.

13. The method of claim 12 wherein said step of selecting includes the step of:

using a number of carriers for transmitting said OFDM symbols and a different number of carriers for receiving said communication signals.

14. The method of claim 11 wherein said step of dynamically changing said downlink data rate includes the step of:

dynamically changing the number of carriers for said communication signals.

28. The method of claim 1, wherein the scalable operating characteristic is transmission rate, and said step of dynamically scaling adaptively selects an operating parameter scaling option which is suitable for the delay-spread characteristic of the communication environment to which said method is applied.

15. A method of receiving orthogonal frequency division multiplexed (OFDM) symbols according to operating parameters, said operating parameters including symbol duration, guard time interval, number of OFDM carriers, and number of bits per symbol per OFDM carrier, said method comprising the step of:

receiving an OFDM signal that includes OFDM symbols;

generating a feedback signal based on said OFDM signal and providing said feedback signal to dynamic control circuitry that determines whether an operating characteristic of OFDM symbols should be changed based on said feedback signal, said operating characteristic being at least one of transmission rate, signal-to-noise ratio, and delay-spread tolerance; and

dynamically changing at least one of said operating parameters for said method of receiving, thereby enabling said method to receive OFDM symbols provided in accordance with dynamically scaled operating characteristics.

17. The method of claim 15 wherein said step of dynamically changing includes the step of:

dynamically changing symbol duration for the OFDM symbols.

18. The method of claim 17 wherein said step of dynamically changing further includes the step of:

altering a time base for a fourier transformation.

16. A method of receiving orthogonal frequency division multiplexed (OFDM) symbols at a downlink data rate according to operating parameters, said operating parameters including symbol duration, guard time interval, number of OFDM carriers, and number of bits per symbol per OFDM carrier, said method comprising the steps of:

receiving an OFDM signal that includes OFDM symbols at a downlink data rate;

generating a feedback signal based on said OFDM signal, and providing said feedback signal to dynamic control circuitry that determines whether an operating characteristic of received OFDM symbols should be changed based on said feedback signal, said operating characteristic being at least one of transmission rate, signal-to-noise ratio, and delay-spread tolerance; and

dynamically changing said downlink data rate by adaptively selecting one of a plurality of operating parameter scaling options.

19. The method of claim 16 wherein said step of dynamically changing includes the step of:

dynamically changing the number of carriers for said OFDM symbols.

20. The method of claim 16 wherein said step of dynamically changing includes the steps of:

decoding said OFDM symbols according to a coding rate; and

dynamically changing said coding rate.

21. An orthogonal frequency division multiplexing (OFDM) system for providing communication signals according to operating parameters, said operating parameters including symbol duration, guard time interval, number of OFDM carriers, and number of bits per symbol per OFDM carrier, said system comprising dynamic control circuitry which receives a feedback signal from a receiver, determines whether an operating characteristic of said method should be scaled from a first level to a second level based on said feedback signal, said operating characteristic being at least one of transmission rate, signal-to-noise ratio, and delay-spread tolerance, and, after determining that said operating characteristic for providing communication signals should be scaled from said first level to said second level based on said feedback signal, provides control signals to signal circuitry to dynamically scale at least one of said operating parameters to achieve said operating characteristic of said second level, said control circuitry controlling a scalable operating characteristic by adaptively selecting one of a plurality of operating parameter scaling options.

22. The OFDM system of claim 21 wherein said signal circuitry transforms said communication signals into OFDM symbols having a symbol duration and transmits said OFDM symbols at a data rate, said dynamic control circuitry provides control signals to dynamically change said symbol duration for said OFDM symbols.

23. The OFDM system of claim 21 wherein said signal circuitry transforms said communication signals into OFDM symbols using a fourier transformation, said dynamic control circuitry provides control signals to dynamically alter a time base for said fourier transformation.

24. The OFDM system of claim 21 wherein said signal circuitry transforms said communication signals into OFDM symbols onto a number of carriers, said dynamic control circuitry provides control signals to dynamically change the number of carriers for said OFDM symbols.

25. The OFDM system of claim 21 wherein said signal circuitry codes communication signals according to a coding rate, said dynamic control circuitry provides control signals to dynamically changes said coding rate.

26. The OFDM system of claim 21 wherein said signal circuitry includes transmitter circuitry which transmits said communication signals at an uplink data rate and receiver circuitry which receives said communication signals at a downlink data rate, said dynamic control circuitry provides control signals to dynamically change said downlink data rate.

27. The OFDM system of claim 21 wherein said signal circuitry includes transmitter circuitry which transmits said communication signals at an uplink data rate using a number of carriers and receiver circuitry which receives said communication signals at a downlink data rate using a different number of carriers, said dynamic control circuitry provides control signals to dynamically change said number of carriers and said different number of carriers.

29. The system of claim 21, wherein said dynamic control circuitry adaptively selects an operating parameter scaling option which is suitable for the delay-spread characteristic of the communication environment to which said system is applied.